Complex kinetics

Hi all guys
I'm dealing with a problematic kinetics issue.. Our theory for this kind of binding is that we think that molecule A bind to Molecule B (the receptor) first with a weak interactions really fast and easy to occur but really fast to disappear (high k-on and k-off) and then with a second interaction (that can occur only after the first one) with a slow k-on and slow k-off. To complicate more we think that the two different bounds are located in two differents molecule of the receptor B.
Something like A+B give AB and then AB+B to give a "stable" complex ABB. where the binding sites are differents in A and B for the two's differents associations.
Any one can help me to find a way to fit this kinetic?
Thanks

It won't be easy, you'll probably have to develop your own model for this kind of interaction. Be aware that models with more parameters usually yield better fitting.
I think Clamp has a Dimerizing analyte kinetic model, you could start by checking it.

Some questions:
- Which equipment you're using?
- Which evidence do you have for this reaction scheme you proposed?
- Which molecule you have immobilized: A or B ?
- Have you tried to immobilize the other molecule? If you can immobilize molecule B you can use molecule A as analyte and solve half the problem.
- Where are you from?

Regards.
Napo

Thanks for ur reply.
Some answers:
I work with a Biacore 3000, I immobilize the receptor B (the active part of it); the evidences we have are that in solution the complex is formed only with a stoichiometry 2:1 or higher (b:a).
Moreover if i try to bind low amount of B (i mean 150 RU the density suggested for kinetics exp) i don't see any significant binding/interactions, that rise as the density rise.
I work in CA but i'm italian.
Best
Alessandro